Historically, transthoracic Doppler echocardiography has been unable to provide interpretable data of blood flow within the lung parenchyma because of air attenuation of Doppler signals. Recently, a transthoracic Doppler system known as the Sonara/tek Transcranial Doppler (TCD) System has been developed that can identify parenchymal pulmonary blood flow (PPBF) signals. The ability to non-invasively collect information regarding the pulmonary aspect of the cardio-pulmonary system may provide valuable information and new insights into the structural and functional characteristics of the lung parenchyma and vasculature in health and disease states.